The field of the invention is the projection of video and computer generated images to a patient positioned within medical imaging systems such as MRI or PET scanners.
Positron emission tomographic (PET) scanners have been used for many years to produce images which show areas of the brain that are active while the subject performs specific functions or is stimulated by sight, sound, smell or touch. More recently, as described in co-pending U.S. patent application Ser. No. 08/005,723 entitled "Time Course MRI Imaging Of Brain Functions", similar images are now produced with magnetic resonance imagers (MRI). In both cases the apparatus required to visually stimulate the subject must operate under severe conditions due to the environments in which they are used. In the case of MRI, for example, the subject's head may be positioned in the very confined opening of a head coil and the apparatus is subjected to very intense magnetic fields (i.e. 0.5 to 3.0 Tesla). As a result, the video apparatus must feed the visual information to the patient and it must not contain any ferromagnetic materials. Indeed, because of the rapidly switched magnetic field gradients required in MRI, no conductive material can be used because such materials will support Eddy currents that distort the magnetic fields required for accurate imaging.
To study the brain it is necessary to stimulate the subject with a wide range of colors and brightnesses that can be accurately controlled. In addition, it requires that the subject be stimulated over a wide field of view and that three dimensional images be presented. For example, a field of view of 15.degree., typical of commercially available binoculars, stimulates on 25% to 30% of the brain areas associated with vision, whereas a field of view of 60.degree. stimulates 80% to 85% of these areas.